Ambient temperature is the temperature that you see on the thermometer when using it outside. This reading does not take into account humidity or wind speed.
When there is a lot of humidity in the air, it can feel hotter than what the ambient temperature is. For example, the thermometer might show 90 degrees, but when meteorologists factor in the humidity, the heat index (the temperature it feels like) can be over 100 degrees.
During the winter, the wind speed is factored in to determine the wind chill. For example, the temperature can feel like 10 degrees when the thermometer shows 30 degrees.